Microsoft this week was about to relent and allow the (legal) virtualization …

The scuttlebutt this week has been that Microsoft was about to relent and allow the virtualization of Windows Vista Home Premium and Home Basic. Since the launch of Windows Vista, only Business and Ultimate editions have been legally approved for virtualization, thanks to the Vista EULA. A change in the EULA was forthcoming, according to embargoed information from the company, and it was a change that I think everyone believed should be made.

Microsoft had gone so far as to reach out to media to pump up the news of the licensing change, issuing a prepared statement in advance of the announcement that said, in effect, that Microsoft heard the voices crying out for support and changed its mind in favor of user "choice." That announcement was supposed to be made today.

Then the announcement never came. Microsoft pulled the plug on the changes just yesterday, and everyone is left wondering why. Microsoft scored some serious positive karma when the company relented on its transfer limitations in its retail license, so why would the company ditch a similar smart move? Mary Jo Foley says that Microsoft informed her via e-mail that "Microsoft has reassessed the Windows virtualization policy and decided that we will maintain the original policy announced last Fall." My usual sources aren't privy to any more detail than that, but I can you that disappointment abounds.

The prohibition against running Vista Home Basic or Home Premium in a virtual machine is easily one of the most disappointing features of Microsoft's end-user license for Windows Vista. It's a move that has frustrated PC enthusiasts and particularly Mac OS X users, many of whom (believe it or not) would like to be able to legally run Home Basic or Premium in a VM. Users were outraged that Microsoft expected them to pony up for more expensive copies of Vista Ultimate or Business, just to get the legal okay to run in a VM.

The situation is made all the more frustrating since Microsoft has provided no compelling technological reason for the prohibition. Cynics say that this is Microsoft's way of punishing Mac switchers, while Microsoft calls it a "security" issue.

For its part, Microsoft says that hypervisor rootkits are a serious threat to virtualization, and they could be right. In theory, such a rootkit would be undetectable to a guest OS, and thus it could operate unknown to users. But as a reason for the licensing discrepancy, we're not buying it. The threat of hypervisor malware affects Ultimate and Business editions just as much as Home Premium and Basic. As such, the only logical explanation is that Microsoft is using pricing to discourage users from virtualizing those OSes. Since when is a price tag an effective means of combating malware?

According to a Microsoft statement issued earlier this year, the prohibition stems from the fact that virtualization "is not yet mature enough from a security perspective for broad consumer adoption." Apparently if you want to get the "maturity" needed to virtualize Vista, it can be had for the $60+ premium that Business costs over and against Home Premium.

The good news from all of this is that Microsoft does appear to be listening, and the company came really close to changing its mind. Perhaps renewed attention to the matter will push them over the hump, and this questionable prohibition can be dropped on the ash heap once and for all. C'mon, Microsoft, if you're worried about hypervisor rootkits that much, educate the public on the matter and let us decide what constitutes safe virtualization security practices.

Ken Fisher / Ken is the founder & Editor-in-Chief of Ars Technica. A veteran of the IT industry and a scholar of antiquity, Ken studies the emergence of intellectual property regimes and their effects on culture and innovation.